A technique for recognizing a traffic environment is absolutely necessary in order to achieve a safety system for a vehicle. Since vehicles, motorcycles, pedestrians, and various other objects appear in the traffic environment, it is necessary to develop an algorithm for recognizing a plurality of objects. In addition, when the problems of the recognition technique are considered, it is necessary to classify the vehicles into a plurality of categories, such as ordinary cars, large-sized vehicles including buses and trucks, and special vehicles. When a change in a viewing direction or the position of the pedestrian is considered, the problems of image recognition need to be considered while the viewing direction and the position of the pedestrian are classified into different categories.
In general, when plural kinds of object recognition (multi-class recognition) are performed, recognition devices for 2-class recognition are combined with each other to achieve object recognition. For example, eight patterns, such as the front surface, right anterior oblique, right lateral, right posterior oblique, rear surface, left posterior oblique, left lateral, and left anterior oblique of the ordinary car, are prepared. In addition, these patterns are prepared for a truck, a bus, a special vehicle, and a motorcycle. For the pedestrian, about eight patterns need to be prepared for, for example, a change in the position of the pedestrian in addition to the direction. Therefore, a large number of recognition devices for 2-class recognition are needed in order to recognize all objects.
However, the time required to recognize the object increases in proportion to at least the number of objects to be recognized. Therefore, this technique is disadvantageous when an immediate response is required, as in a vehicle recognition technique. In addition, since it takes a long processing time and a large number of recognition devices for 2-class recognition need to be prepared, it takes a long development time or the capacity of programs or dictionaries stored in an ECU is likely to increase.
Non-patent Literature 1 discloses a technique which recognizes the class of an object, such as a vehicle or a pedestrian, on the basis of a captured image, without using a recognition device for 2-class recognition.